1. Field of the Invention
The present invention relates to a time-division multiplex communication control circuit for an ATM (Asynchronous Transfer Mode) terminal, and more particularly to a time-division multiplex communication control circuit for an ATM terminal which carries out time-division multiplex communications in a network which has no multiplexer on a circuit line.
2. Description of the Related Art
For effecting time-division multiplex communications between a plurality of terminals in a network with ATM, it is necessary to multiplex information generated by the terminals according to a time-division multiplex process in order to transmit the information over a single circuit line.
Time-division multiplex communication control circuits for controlling such time-division multiplex communications are used to transmit the multiplexed information from the terminals over the single circuit line. Conventional time-division multiplex communication control circuits require that a multiplexer be provided on the circuit line.
For example, Japanese Patent Laid-Open No. 114912/93 discloses a time-division multiplex communication control technique for synchronizing information generated by a plurality of mediums in a system which has a multiplexer on a circuit line.
Since the multiplexer needs to be provided on the circuit line, the conventional time-division multiplex communication control circuits cannot use a circuit line of a network which has no multiplexer on the circuit line, such as a circuit line of an existing CATV (CAble TeleVision) network, directly as an ATM circuit line, or use such a circuit line as both an ATM circuit line and a circuit line for originally intended use.
The reasons for the above problem are as follows: A plurality of terminals of a network operate independently of each other and generate their own items of information out of synchronism with each other. The items of information generated by the respective terminals overlap each other in time. If the overlapping items of information were transmitted over the circuit line without being multiplexed, then they would conflict each other on the circuit line.